electrical box fill

[Sam Takoy]

Hi,

I have an old-work 20 cu in junction box. It has two sets of 14-2 cables spliced: two sets of travelers weren't long enough and had to be lengthened.

The box uses Ideal connectors which take very little space. All and all, the wires already in there take about 1/4 of the available space.

I need to add an outlet to that box (same circuit) which I'm technically not allowed to do. However, practically speaking, the box will hardly be half full if I do this.

What would you do in this situation?

Thanks!

Sam

[jw]

You didn't say why you're "technically not allowed to do this"? I can only assume you said it because local code dont allow a non-licensed electrician to do the work. (Which is rare if the homeowner does his own work). So, without knowing this reason, I can only say that if this was *MY HOUSE*, I'd just add the outlet and shut up about doing it.Inspection departments cant possibly keep a record of every outlet in every home. If someone ever asks about it, just tell them it was there when you bought the house. (Of course be sure to do it according to the code, which mostly just means adding a bare or green grouns wire, and splicing with the approved wirenuts, not tape). ANd use the same gauge of wire too.

[Nate Nagel]

If it's an old work box why not take it out and use a deeper one?

you say "travelers" but then you mention 14/2... is this a 3-way switch circuit?

nate

[Sam Takoy]

OK, some clarification.

I'm technically not allowed to do this because that would be too many wires/devices. 20 cu in is the deepest single gang box available. And with two sets of 14-2 wires spliced, I used up 17 cu in of nominal space (2x4x2 + 1).

Yes, it's a 3-way/4-way switch circuit, but the neutral is delivered to the electrical box with the switches by a different cable that does not pass through this junction box.

So: by adding a 14-2 wire and an outlet to this box, I will technically be going over the wire limit. But practically, the box will only be about half full.

[Nate Nagel]

Ah, I got you. So you are going to have to pull another cable into the box, that is what I was missing.

Do you have access to the backside of this wall? could you use a 1900 (4" square) box with a mud ring?

nate

[Sam Takoy]

Yes, I have access to the back, but I can't replace the box. It's tightly between two studs.

[dpb]

...

...

...

As another poster said, given the description and particularly that it's

14-ga wire that is so flexible, I'd in all likelihood go ahead and stretch the volume limit if it was truly near-impossible to retrofit the larger box for some reason (other than just not wanting to do so).

While it might not be totally Code-compliant, if the conductors are not kinked or rubbing on mount screws, etc., it is not going to be a safety problem.

I've seen many, many boxes over the years that are absolutely crammed to the limit of what could be gotten into them and none have ever been a problem owing to that capacity limit.

So, it isn't quite kosher, but sometimes "ya' just gotta' do what ya' gotta' do" when it isn't really going to be anything but a technical violation, not a safety one.

$0.02, etc., etc., etc., ...

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[Doug Miller]

Where does that "+ 1" come from?

Here's what your calculation *should* look like:

4 14ga cables @ 2 conductors each = 8 conductors add 1 for one or more equipment groundi ng conductors add 1 for each cable clamp in use (presumably at least 2)

That's what you have *already*: the equivalent of 11 conductors, at 2 in^3 each, which means you're at 22 in^3 *now*. Not 17.

Then add 2 more for the device yoke you're planning to add. That brings the total to 13 conductors x 2 in^3 each = 26 in^3 minimum.

[Wayne Whitney]

While that is permitted with nonmetallic cable (Romex), it will cause some EMI when the light on, since the neutral is not routed with the hot conductors. It is generally a good practice to route your cables together when the neutral and the hot/travelers are in different cables.

As to your OP, if I couldn't possibly fit a larger box there, I'd use an additional box for the receptacle. And I'd feed it with a hot and neutral together in the same cable.

Cheers, Wayne

[Wayne Whitney]

That's his allowance for the EGCs, but it's not quite right. It should be (2 * 4 + 1) * 2, or 18 in^3.

You only need to count clamps that extend into the box, so the integral clamps on a plastic box do not need to be counted. Thus I assume he's using a plastic box.

Plus, since we are talking about a one-gang box, for a plastic one-gang and NM cable, you don't need to clamp the wire to the box, as long as you secure the wire close enough to the box (I forget the requirement). Single-gang plastic boxes typically don't have cable clamps at all.

Cheers, Wayne

[Wayne Whitney]

You can definitely get them up to 24 in^3, although they will obviously be bigger in some dimension and so might not fit in your space. See, for example,

But you need 26 in^3 for what you want to do, and I don't know if those exist.

Cheers, Wayne

[RBM]

Also, there are 22cu. in. plastic single gang boxes, or he could use a deep plastic 1900 box with single gang reducing cover. Then he can go hog wild.

[bud--]

I didn't entirely follow that from Sam, but all wires for a circuit need to appear in the same cable; it seems to violate 310.3-B. I would consider that more important than too many wires in the box. Sounded like Sam was also considering adding a romex and an outlet in the box.

Another possible, but ugly, is a wiremold surface extension.

Anonymously ask the inspector his opinion about overfill in this box?

Box now has a blank cover?

[Wayne Whitney]

I assume you mean 300.3(B). In which case see 300.3(B)(3), which basically says the requirement doesn't apply to cables with a non-metallic sheath, i.e. Romex. None the less, when circuit conductors are split between multiple cables, it is a good idea to run the cables together.

Cheers, Wayne

[Doug Miller]

I, on the other hand, having observed that he didn't calculate the EGC requirement correctly, just assumed he didn't know he was supposed to count the clamps too.

Right, but I don't think he ever stated explicitly that it's a plastic box. OTOH, he *did* state explicitly that it's an old work box -- which makes it

*very* unlikely that the cables are secured to the framing at all, let alone within the required distance (which, BTW, is 8 inches).

[bud--]

Yes - a typo.

300.3 was rewritten a few codes ago and I had a distinct recollection that California 3-ways that used 2 2-wire romexes were prohibited. Looks like the weren't.

If the conductors are not together and with high current the magnetic field from the loop can affect CRTs, as in old TVs. I guess CRTs are rapidly disappearing.

[jw]

Why even bother thinking about this. No neutral means that you can NOT put an outlet in there no matter how much box space is used. Put the cover back on the box and put in a different box with a new run of cable for your new outlet. You can put this new outlet near the old box, or anywhere else you want it.

As a side note, the neutral most likely goes to the light fixture directly and this box is used for the wires feeding a switch.

End of topic.